The present invention relates to a method of controlling a hybrid electric automotive powertrain and in particular to a method of timing transmission gearing shifts.
A hybrid electric powertrain of an automotive vehicle may include both an internal combustion engine and an electric machine to provide propulsion. Commonly, while the vehicle is maintaining a constant cruising speed, the powertrain will stop the engine and use only the machine for propulsion. While at the machine only cruising speed, an acceleration request may be made. Meeting the acceleration request may require both restarting the engine and downshifting a transmission.
However, the combination of restarting the engine and downshifting may result in a torque shortage that delays meeting the acceleration request. The torque shortage may reduce drivability by causing a driver of the vehicle to experience a sense of deceleration despite making the acceleration request.